|Excess Fat Around the Waist May Increase Death
Risk For Women
Women who carry excess fat around their waists were at greater
risk of dying early from cancer or heart disease than were women
with smaller waistlines, even if they were of normal weight, reported
researchers from Harvard and the National Institutes of Health.
Previous studies have shown that the tendency to deposit fat around
the waist increases the risk for health problems. The current study
is the largest, most comprehensive of its kind undertaken to show
that accumulation of abdominal fat can increase the risk of death.
To conduct the study, the researchers analyzed data from more
than 44,000 women in the Nurses’ Health study, which followed the
health history of thousands of registered nurses in 11 states.
"As we know from the work of the NIH Obesity Research Task
Force, reversing the epidemic of obesity is challenging," said
Elias A. Zerhouni, M.D., Director of the National Institutes of
Health. "The current findings highlight the role that research
can play in understanding the risks of obesity."
The research team that conducted the study was led by Cuilin Zhang,
M.D., Ph.D., of NIH’s Eunice Kennedy Shriver National Institute
of Child Health and Human Development (NICHD). Dr. Zhang conducted
much of her work on the study while at the Harvard School of Public
Health. She concluded her analysis after joining the staff of the
NICHD. The study was conducted in the research group of Dr. Frank
Hu, M.D., Ph.D., of the Harvard School of Public Health, and by
researchers from Brigham and Women’s Hospital and Harvard School
Funding for the study was provided by the NIH’s National Institute
of Diabetes and Digestive and Kidney Diseases and the National
Cancer Institute. The Nurse’s Health Study was supported by NIH’s
National Heart, Lung and Blood Institute.
The study was published online in Circulation.
There is increasing evidence that excess abdominal fat is a risk
factor for long-term conditions like diabetes and heart disease.
However, the relationship between abdominal obesity and risk of
death has not been widely studied. The current study is one of
the largest extended investigations of abdominal obesity and women’s
risk of premature death.
Researchers followed more than 44,000 women over the course of
16 years to track their medical history and lifestyle. Because
the majority of the women who took part in the study were white,
the researchers do not know if their findings pertain to other
groups of women or to men.
All the women included in the study were registered nurses. At
the beginning of the study the women were asked to measure their
waists and hips. Every two years, the women completed questionnaires
about their health, providing information about their age, activity
level, smoking status, diet, blood pressure and cholesterol levels.
The researchers examined the cause of death for all women who
died over the course of the study. In total, 3,507 deaths occurred — of
these, 1,748 were due to cancer and 751 were due to heart disease.
The researchers discovered that women with greater waist circumferences
were more likely to die prematurely, particularly from heart disease,
when compared to women with smaller waists. For example, women
with waist size equal to or greater than 35 inches were approximately
twice as likely to die of heart disease as were women with a waist
size less than 28 inches, regardless of their body mass index.
Similarly, women with a waist size equal to or greater than 35
inches also were twice as likely to die of cancer as were women
with a waist size less than 28 inches.
Women who had a greater waist circumference and were also obese
were at the greatest risk of premature death. Researchers determined
if a woman was overweight by calculating her body mass index (BMI),
a measure of a person’s weight in relation to height. BMI is used
to estimate the proportion of a person’s weight that derives from
body fat. A BMI between 18.5 and 24.9 is considered healthy. A
BMI of 30.0 - 39.9 is regarded as obese.
Greater waist circumference is a sign of collecting excess fat
around one’s midsection, called abdominal obesity. According to
the Clinical Guidelines on the Identification, Evaluation and
Treatment of Overweight and Obesity in Adults published by
NHLBI in cooperation with NIDDK in 1998, a healthy waist limit
for women is 35 inches and, for men, 40 inches. Waist circumference
is determined by measuring around the waist at the navel line.
The NHLBI lists information on waist circumference and BMI at http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm
In 2004, over one-half of U.S. adults had abdominal obesity by
these standards, said Dr. Zhang.
The researchers also studied waist-to-hip ratio — a measure
of the narrowest part of the waist compared to the circumference
at the broadest part of the hip — as a potential determinant
of mortality risk. Waist-to-hip ratio was found to be as strongly
associated with risk of early death as the measurement of waist
size alone. However, waist-to-hip ratio requires two measurements
and therefore may be less convenient to calculate than measuring
waist circumference alone, said Dr. Zhang.
The study authors wrote that results from previous studies have
been inconsistent because of the relatively small number of people
who took part and the short duration of the studies. The current
study provides the strongest evidence so far regarding the adverse
effects of abdominal obesity on the risk of death in women. The
authors called for future studies to investigate abdominal obesity
and the risk of death in men and other ethnic groups.
"Although maintaining a healthy weight should continue to
be a corner stone in the prevention of chronic diseases and premature
death, maintaining a healthy waist size should also be an important
goal," the study authors wrote.
Learn more about weight control, obesity, physical activity, and
related nutritional issues from NIDDK’s Weight-control Information
Network at http://win.niddk.nih.gov.
For Weight and Waist Measurement: Tools for Adults, visit http://win.niddk.nih.gov/publications/tools.htm.
Learn more about ways to maintain a healthy weight based on the
Clinical Guidelines Expert Panel Report, visit the NHLBI’s Aim
for a Healthy Weight Web site http://healthyweight.nhlbi.nih.gov.
To calculate your BMI and assess your risk for conditions related
to overweight and obesity, visit http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm.
Information about obesity, weight, physical activity, diet, and
cancer is available at. http://www.cancer.gov/cancertopics/energybalance.
Information about the Nurse’s Health Study is available at http://epi.grants.cancer.gov/ResPort/NursesHealthI.html.
The NICHD sponsors research on development, before and after birth;
maternal, child, and family health; reproductive biology and population
issues; and medical rehabilitation. For more information, visit
the Institute’s Web site at http://www.nichd.nih.gov/.
The National Institute of Diabetes and Digestive and Kidney Diseases,
a component of the NIH, conducts and supports research in diabetes
and other endocrine and metabolic diseases; digestive diseases,
nutrition, and obesity; and kidney, urologic, and hematologic diseases.
Spanning the full spectrum of medicine and afflicting people of
all ages and ethnic groups, these diseases encompass some of the
most common, severe, and disabling conditions affecting Americans.
For more information about NIDDK and its programs, see www.niddk.nih.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.